Gas valve operator drive circuit

ABSTRACT

A water heater comprising a thermoelectric device to power components of the water heater, a valve configured to control gas flow, and a controller. The controller may be configured to periodically determine one or more electrical parameters for holding the valve in the open state. The controller may be configured to alter the one or more parameters with the valve in an open state until the valve deviates from the open state. The controller may cause a current to flow through the valve based on the determined one or more electrical parameters.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/886,746 (filed Aug. 14, 2019), which isentitled, “GAS VALVE OPERATOR DRIVE CIRCUIT” and incorporated byreference herein in its entirety.

TECHNICAL FIELD

The disclosure relates to water heating systems.

BACKGROUND

Tank-type water heating systems which incorporate gas combustion as aheat source typically utilize a pilot flame issuing from a pilot burnerto initiate combustion of a main gas flow. Combustion of the main gasflow initiates a flame at a main burner. The main burner flame typicallyheats a volume of water. A temperature sensing device in thermalcommunication with the volume of water may provide a temperature to acontrol system to serve as an indication of when pilot flame and mainburner flame may be desired. The control system may initiate operationswithin the water heater system to initiate the pilot flame and the mainburner flame by, for example, energizing valve actuators in order toestablish the necessary gas flows to one or more dormant burners.

SUMMARY

The water heater system disclosed herein provides for the periodicdetermination of one or more electrical parameters required to maintaina one or more valves in an open position. The periodic determination ofthe one or more electrical parameters allows the control system tojudiciously supply power in an efficient manner, such that energysignificantly beyond what may be required for a specific valve operationis not expended. This may be beneficial when the water heater controlsystem relies on a stored energy system or a thermoelectric device tosupply operating power, rather than power from a line source external tothe water heater.

The water heater system comprises at least a thermoelectric device, avalve, and a controller. The thermoelectric device may convert thermalenergy into electrical energy and power one or more components of thewater heater. The valve is configured to control whether there is a gasflow to cause a flame. The gas flow may be a main gas flow and the flamemay be a main burner flame caused by thermal communication between apilot flame and the main gas flow. In some examples, the gas flow may bethe pilot gas flow and the flame may be the pilot flame. In someexamples, the thermoelectric device converts thermal energy from thepilot flame into electrical energy.

The controller may be configured to receive power from the electricalenergy generated by the thermoelectric device. The controller may beconfigured to receive power from a from a power source such as a batteryor capacitor. The power source may be a non-rechargeable battery orpre-charged capacitor having a life that lasts as long as a life of thewater heater device. The controller may periodically determine one ormore electrical parameters for holding the valve in an open state. Theone or more electrical parameters may be a voltage amplitude provided tothe valve (e.g., to a solenoid or other electrical component comprisingthe valve), a current amplitude provided to the valve, or a voltageamplitude and a current amplitude provided to the valve. The controllermay periodically determine the one or more electrical parameters basedat least in part on information indicative of whether the valve is inthe open state. The controller may cause a current to flow through thevalve (e.g., through a valve actuator) based on the determine one ormore electrical parameters. In an example, the valve is a solenoid valveactuated by a solenoid, and the controller causes a current to flowthrough the solenoid in accordance with the determined one or moreelectrical parameters.

The controller may be configured to determine an amount of energygenerated by the thermoelectric device, and the information indicativeof whether the valve is in the open state may be an amount of energygenerated by the thermoelectric device. The indicative information maybe an increase or a decrease in the electrical energy generated by thethermoelectric device. In some examples, when the valve controls whetherthere is a pilot gas flow causing a pilot flame, a decrease in theelectrical energy generated may indicate the valve is no longer in theopen state (e.g., the valve has deviated from the open state). In someexamples, when the valve controls whether there is a main gas flowcausing a main burner flame, an increase in the electrical energygenerated may indicate the valve is no longer in the open state.

The controller may be configured to determine one or more of a voltagesupplied to the valve, an inductive signature associated with the valve,or a current supplied to the valve. The information indicative ofwhether the valve is in the open state (or has deviated from the openstate) may be at least one of the voltage supplied to the valve, theinductive signature of the valve, or the current supplied to the valve.

In examples, the valve is configured to hold in an open state whilereceiving a holding amount of the one or more electrical parameters. Theholding amount may be a voltage amplitude provided to the valve, acurrent amplitude provided to the valve, or a voltage amplitude and acurrent amplitude provided to the valve. The holding amount may be avoltage amplitude, a current amplitude, or a voltage amplitude and acurrent amplitude provided to the valve which results in a holdingcurrent flowing to the valve. The controller may be configured toprovide the holding amount to the valve and hold the valve in the openstate. With the valve in the open state, the controller may determine adropping amount by altering one or more of the electrical parametersuntil the valve deviates from the open state. The holding amount may bea voltage amplitude, a current amplitude, or a voltage amplitude and acurrent amplitude provided to the valve which results in a droppingcurrent flowing to the valve. The controller may revise the holdingamount of the one or more electrical parameters for the valve based onthe dropping amount, and thereby periodically determine the one or moreelectrical parameters for holding the valve in the open state.

In this manner, the controller may recognize when the electrical powerrequired to hold a specific valve open has decreased due to, forexample, mechanical wear, changes in environmental conditions, or someother reason. This can provide advantage in scenarios where poweravailability may be limited. The system may be configured tosubsequently utilize the determined electrical parameters for thespecific valve going forward, so that the energy savings associated witha reduced hold current can be realized.

The water heater system may further comprise a temperature sensor. Thecontroller may be configured to receive a reference temperature signalfrom the temperature sensor when the controller periodically determinesand revises the holding amount of the one or more electrical parametersnecessary to hold open the valve. The controller may associate thedetermined one or more electrical parameters with the referencetemperature signal. Going forward, when operation of the valve isrequired, the controller may receive an environmental temperature signalindicative of a present environmental temperature, and cause current toflow through the valve based at least in part on the environmentaltemperature signal.

In examples, the valve is a main valve controlling whether there is amain gas flow. The main gas flow may be in thermal communication with apilot flame to generate a main burner flame. The water heater may be anintermittent pilot system further comprising an pilot valve controllingwhether there is a pilot gas flow to generate the pilot flame. Thecontroller may be configured to periodically determine a holding amountof the one or more electrical parameters for each of the main valve andthe pilot valve.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a pilot light and appliance burner integration ina water heater system.

FIG. 2A is an example pilot valve and main valve apparatus with a pilotservo valve and main servo valve in a closed position.

FIG. 2B is the example pilot valve and main valve apparatus with thepilot servo valve in an open position and the main servo valve in aclosed position.

FIG. 2C is an example pilot valve and main valve apparatus with thepilot servo valve and the main servo valve in the open position.

FIG. 3 is an example of a control system for an intermittent pilot waterheater.

FIG. 4 is an example of a control system configured to periodicallydetermine one or more electrical parameters of a valve.

FIG. 5 is an example technique for determining one or more parametersrequired to hold a valve in an open state using a controller.

DETAILED DESCRIPTION

The water heater control system disclosed herein provides a controllerconfigured to periodically determine one or more electrical parametersrequired to hold a valve in an open position, and then subsequentlyapply the determined one or more electrical parameters when operation ofthe valve is required. This periodic determination provides a capabilityfor the control system to recognize when the power requirements forholding open a specific valve may have increased or decreased. Thisallows the controller to judiciously supply power in an efficientmanner, such that energy significantly beyond what may be required for aspecific valve operation is not expended. This may be beneficial whenthe water heater control system relies on a stored energy system or athermoelectric device to supply operating power, rather than power froma line source external to the water heater.

A control system may benefit from a controller being configured toperiodically determine one or more electrical parameters required tomaintain one or more control valves in an open position, and thensubsequently apply the one or more electrical parameters when controlvalve operation is required. The electrical power sufficient to maintaina given control valve open may decrease over the life and continuedoperation of the control valve due to mechanical wear, changes inenvironmental conditions, or other reasons. In a system which may relywhole or in part on a limited power supply, periodic evaluation andsubsequent application of the sufficient power level for opening andholding open a specific control valve can mitigate excessiveexpenditures of the limited power available. Additionally, periodicallydetermining and subsequently providing the sufficient levels of powermay increase the availability of electrical power for other poweredcomponents either within the control system or elsewhere in a waterheating system, as opposed to uniformly applying predetermined powerlevels throughout the life of a control valve.

The one or more valves may be control valves within a water heatingsystem. For example, a first control valve such as a pilot servo valvemay be configured to cause a pilot gas flow to issue from a pilotburner, while a second control valve such as a main servo valve may beconfigured to cause a main gas flow to issue from a main burner. Eachvalve may be operated via electrical power provided to a specific valveoperator. For example, a control valve may be a solenoid operated valvecomprising a solenoid, and the solenoid may be the specific valveoperator.

The water heater control system provides for periodic determination ofone or more electrical parameters required to maintain a control valvein an open position. Generally, the control valves are configured suchthat remaining in an open position is necessary to execute desiredoperations of the water heater. For example, the water heater may be anintermittent pilot system where a pilot servo valve is required to openand remain open in order to provide a pilot gas flow to a pilot burner,so that a pilot flame may be generated and sustained through theduration of some desired operating period. Similarly, a main servo valvemay be required to open and remain open in order to provide a main gasflow to a main gas burner, so that a main burner flame may be generatedand sustained until completion of the desired operating period. Closureof the pilot servo valve or the main servo valve before elapse of thedesired operating period may result in premature termination of the mainburner flame. Consequently, electrical power must be supplied to boththe pilot servo valve and the main servo valve throughout the desiredoperating period.

In many control systems responsible for control valve operation, thenecessary electrical parameters such as a current and/or voltagerequired to establish a control valve in an open position is initiallydetermined either through testing or a manufacturer specification, thenapplied uniformly throughout the life of the control valve. However, insome cases, the electrical power required to maintain a given controlvalve open may decrease over the life and continued operation of thecontrol valve, due to mechanical wear, changes in environmentalconditions, or other reasons. For example, in some solenoid operatedcontrol valves, the holding currents necessary to maintain an openposition might decrease by 3-25 times over the operating life of thecontrol valve. When such changes occur, continuing to apply currentand/or voltage to the control valve based on parameters initiallydetermined at beginning of life can result in providing more power thanis necessary. This can be a distinct disadvantage in scenarios wherepower availability may be limited. The system disclosed herein comprisesa controller configured to periodically evaluate one or more of theelectrical parameters provided to a specific control valve, allowing thecontroller to recognize when these required holding currents havedecreased. The system is configured to determine the one or moreelectrical parameters required for operation of the control valve, andsubsequently utilize the determined electrical parameters for thespecific valve going forward, so that the energy savings associated witha reduced hold current can be realized.

This capability may be important in water heater systems that operate inthe absence of a line voltage provided by an existing energyinfrastructure, such as a line voltage provided to a residence or someother structure served. These water heater systems may be wholly orpartially reliant on a thermoelectric device in order to generatenecessary electrical power for operation. In conjunction with thethermoelectric device, the systems may also include an energy storagesystem to store some portion of the electrical energy generated by thethermoelectric device. The energy storage system may be relied upon foroperations necessary when the thermoelectric device is dormant or notgenerating significant electrical power. The energy storage system maycomprise a battery and/or capacitor. The energy storage system maycomprise a non-rechargeable battery or pre-charged capacitor having alife intended to last as long as a life of the water heater device. Thebattery or capacitor may be replaceable.

As an example, in a control system for an intermittent pilot waterheater, a stored energy system may provide the electrical energy foroperations necessary to establish a pilot flame when pilot flameoperation is called for, due to a call for heat using a main burner orfor some other reason. These operations may include opening and holdingopen a pilot control valve configured to establish a pilot gas flow, andenergizing an ignition circuit in thermal communication with the pilotgas flow to establish a pilot flame, among other possible duties. Acontroller configured to periodically evaluate one or more of theelectrical parameters provided to the pilot control valve, update theone or more electrical parameters required, and subsequently utilize theupdated electrical parameters in future operations may allow the systemto recognize when the required energy for establishing the pilot flamehave decreased, and to take advantage of the reduced power requirementswhich may be available. This may increase the energy budget availablefor other components which may be reliant on the stored energy system,as well as reduce the frequency of charging cycles which may be requireddue to a discharges from the stored energy system.

Once the pilot flame is established, a thermoelectric device in thermalcommunication with the pilot flame may be utilized to generate theelectrical power necessary for additional operations required togenerate a main burner flame. These operations may include opening andholding open a main control valve configured to establish a main gasflow to a main burner, with the main gas flow in thermal communicationwith the pilot flame to establish a main flame. A controller configuredto periodically evaluate one or more of the electrical parametersprovided to the main control valve, update the one or more electricalparameters required, and subsequently utilize the updated electricalparameters in future operations may allow the system to recognize whenthe required energy for establishing the main flame have decreased, andto take advantage of the reduced power requirements. This may increasethe energy budget available for other components which may be reliant onthe thermoelectric device.

FIG. 1 provides an example water heating system which might benefit fromperiodic determination of control valve electrical power requirements.FIG. 1 comprises pilot burner 41 and main burner 42 integrated in awater heater system 70. Fuel line 46 is in fluid communication with amain valve 44, which controls fuel flow to a main burner 42. A flue 50may be an exhaust for main burner 42 in system 70. A pilot valve (notshown) may control fuel flow to a pilot burner 41 through fuel line 58.The pilot valve may be substantially in series, or in some otherarrangement with main valve 44, and fuel to pilot burner 41 may comefrom fuel line 46 or some other source. There may be a pilot sparkignitor 56, for igniting a pilot gas flow discharging from pilot burner54.

There may be a thermoelectric device 66 such as a thermopile connectedby an electrical line 52 to control system 71. In examples, controlsystem 71 may be at least partially enclosed within control housing 72.There may be a pilot spark ignitor 56 for igniting a pilot gas flowdischarging from pilot burner 41. Pilot spark ignitor 56 may beconnected via electrical line 60 to control system 71. Thermoelectricdevice 66 may be in thermal communication with pilot flame generated atpilot burner 41, and may convert some portion of a heat flux emitted bythe pilot flame into electrical energy. A temperature sensing device 62may be connected to control system 71 and situated in a water tank 64,or otherwise be configured to be in thermal communication with a volumeof water in water tank 64. Control system 71 may incorporate amicrocontroller configured to establish electrical or data communicationwith one or more of main valve 44, the pilot valve, and othercomponents.

A control system may include a pilot valve operator configured toactuate the pilot valve of system 70, and may include a main valveoperator configured to actuate main valve 44. The control system mayalso establish an electrical connection between thermoelectric device 66and the main valve operator, such that the main valve operator can bepowered by thermoelectric device 66. The control system may also includean energy storage system in electrical connection with the pilot valveoperator.

In an intermittent pilot light system, when main burner 48 operation iscalled for, an operating sequence in system 70 might initially actuatethe pilot valve and establish a pilot flame at pilot burner 41 prior tocommencing main valve 44 operations. For example, control system 71might initially actuate the pilot valve and pilot spark ignitor 56 usingan energy storage system in order to establish the pilot flame at pilotburner 41. Subsequently, once the pilot flame is established, theoperating sequence might actuate main valve 44 using power delivered bythermoelectric device 66. This operating sequence might be utilized toensure the pilot flame is established prior to initiating main fuel flowto the burner.

In order to maintain the pilot flame, pilot valve 41 may be required tobe held open by a valve operator consuming electrical power. Forexample, a position of pilot valve 41 may be controlled by anelectrically actuated servo valve. Allowing the servo valve to close mayclose pilot valve 41, terminating a pilot gas flow to the pilot burnerand extinguishing the pilot flame. Consequently, when the servo valve isan electrically actuated valve requiring energization to remain open,such as a solenoid valve, the servo valve receives electrical powerthroughout the period a pilot flame is desired. As a result,periodically determining a sufficient level of power necessary to openand hold open the servo valve avoids excessive expenditures ofelectrical power. Similarly, in order to maintain the main burner flame,main valve 44 may be required to be held open by another valve operatorconsuming electrical power. For example, a position of main valve 44 maybe controlled by a second electrically actuated servo valve. Allowingthe second servo valve to close may close main valve 44, terminating amain gas flow to the main burner and extinguishing the main burnerflame. Consequently, when the second servo valve is an electricallyactuated valve requiring energization to remain open, such as a solenoidvalve, the second servo valve receives electrical power throughout theperiod a main burner flame is desired. As a result, periodicallydetermining a sufficient level of power necessary to open and hold openthe second servo valve avoids excessive expenditures by a control systemproviding electrical power to maintain pilot valve 41 and main valve 44in an open position.

As described in more detail, operation of the pilot valve and the mainvalve may be driven by respective pilot valve operators and main valveoperators. Examples of pilot valve operators and main valve operatorsare servo valves (e.g., solenoids), also referred to as milli-volt (mV)operators. The example techniques may be applied to the pilot valveoperators and the main valve operators or directly to the pilot valveand the main valve. Accordingly, the example techniques described inthis disclosure are described with respect to valves, examples of whichinclude the pilot valve operators, main valve operators, pilot valve,and main valve.

Furthermore, utilization of the technique on pilot valve operators andpilot valves may not be necessary in all examples. For instance, in someexamples where water heater system 70 is not an intermittent pilotsystem (e.g., system 70 is a continuous pilot or standing pilot system),pilot burner 41 may be lit substantially continuously, and there may notbe pilot valve operators or pilot valves as specifically discussed withreference to FIG. 1. However, a pilot valve operator or pilot valve maystill be present in examples where water heater system 70 is not anintermittent pilot system. In examples where water heater system 70 isan intermittent pilot system, water heater system 70 includes a pilotvalve operator or pilot valve.

The valves (e.g., pilot valve operators, main valve operators, pilotvalve, and main valve) may operate in accordance with a pick current,hold current, and drop current. The pick current is an amount of currentneeded to move a valve from a closed state to an open state. The holdcurrent is an amount of current needed to keep the valve in an openstate once in the open state. The drop current is a current slightlyless than the hold current at which the valve deviates from the openstate to a non-open state (e.g., closed state). The non-open state maybe a fully closed state where for example a valve disc rests on a valveseat, or may be some state in between the open state and the fullyclosed state. For example, a non-open state may indicate a state thatmight be characterized as only 20% open, or 90% shut, or some otherdescriptor indicating a valve having some status between the open stateand a fully shut state.

As described in more detail, a control system may be configured todetermine the amount of the electrical parameters (e.g., electricalparameter levels) needed to keep the valves in the open state. Forinstance, rather than delivering current at a level much higher than theneeded hold current, which can waste power, the control system maydetermine the electrical parameters needed to deliver the current tokeep the valves in the open state where the amplitude of the deliveredcurrent is approximately equal to the hold current (e.g., equal to thehold current or 10-20% greater than the hold current).

FIGS. 2A-2C illustrates an example pilot valve and main valveconfiguration. At FIG. 2A, diaphragm 124 is illustrated in a closedposition isolating an inlet 122, an intermediate pressure chamber 130,and a pilot outlet 132. Inlet 122 may be in fluid communication with afuel supply and pilot outlet 132 may be in fluid communication with apilot burner. Diaphragm 124 in the position illustrated is isolating thefuel supply and the pilot burner, at least at location 158. Diaphragm124 is acted on by spring member 126, and fluid pressures in inlet 122and chamber 128 are substantially equal, so that diaphragm 124 ismaintained in the closed position. Servo valve 134 is maintaining disc136 in a position isolating conduit 138 and intermediate pressurechamber 130 (intermediate pressure chamber 130 comprises and extendsacross 130 a, 130 b, and 130 c), maintaining the fluid pressures ininlet 122 and chamber 128 substantially equal. Additionally, fluidpressures in inlet 122 and chamber 128 are greater than a pressure atintermediate pressure chamber 130 and pilot outlet 132.

Valve body 120 also has diaphragm 142, and servo valve 152 having disc154. Diaphragm 142 is in a closed position isolating intermediatepressure chamber 130 (comprising 130 a, 130 b, and 130 c) and outlet 148at least at position 160 (outlet 148 comprises and extends across 148 a,148 b, and 148 c). Outlet 148 may be in fluid communication with a mainburner. Diaphragm 142 is acted on by spring member 144, and diaphragm124 is maintained in the closed position at least by spring member 144.The pressure of chamber 130 is equalized with outlet 148 through conduit162.

A pilot valve operator may be configured to cause servo valve 134 toreposition disc 136. In an example, control system 71 may be configuredto energize the pilot valve operator. For example, FIG. 2B illustratesvalve body 120 with servo valve 134 having positioned disc 136 to allowfluid communication between chamber 128 and intermediate pressurechamber 130. This provides at least some venting of the pressure inchamber 128 through first supply orifice 140 and reduces the pressure ofchamber 128. This allows the pressure of inlet 122 to position diaphragm124 into the position shown, where fluid communication between inlet 122and pilot outlet 132 may occur at least at location 158. This allowsfluid communication between inlet 122 and pilot outlet 132, and mayallow a fuel supply to proceed from inlet 122 to the pilot burner.Additionally, with 152 closed, the pressure of chamber 146 issubstantially equalized with intermediate pressure chamber 130 throughconduit 162, and diaphragm 142 remains in the closed position.

With servo valve 134 held open and fuel supplied to a pilot burner, suchas pilot burner 41, an ignitor such as ignitor 56 may establish a pilotflame at pilot burner 41 (FIG. 1). Thermoelectric device 66 in thermalcommunication with the pilot flame may convert some portion of the heatflux emitted by the pilot flame into electrical energy.

Allowing servo valve 134 to close will return diaphragm 124 to theposition depicted in FIG. 2A, terminating the fuel supply to the pilotburner. Consequently, when servo valve 134 is an electrically actuatedvalve requiring energization to remain open, such as a solenoid valve,servo valve 134 receives electrical power throughout the period a pilotflame is desired. As a result, periodically determining a sufficientlevel of power necessary to open and hold open servo valve 134, and thenapplying that level of power to servo valve 134 when a pilot flame iscalled for, avoids excessive expenditures from a control system whenproviding power to servo valve 134. This may be particularly meaningfulwhen an operating sequence calls for electrical power from an energystorage system to open and hold open servo valve 134 until a pilot flamegenerates and a thermoelectric electric device can commence generationof electrical power, or when a control system is wholly or partiallyreliant on a limited power supply to supply all or a large portion ofthe electric power needs required

A main valve operator may be configured to cause servo valve 152 toreposition disc 154. In an example, control system 71 may be configuredto energize the main valve operator. For example, FIG. 2C illustratesvalve body 120 with servo valve 152 having positioned disc 154 to allowfluid communication between chamber 146 and outlet 148 though conduit150. This allows at least some venting of the pressure in chamber 146through second supply orifice 157 and reduces the pressure of chamber146. The venting of chamber 146 through conduit 150 allows the pressureof intermediate pressure chamber 130 to position diaphragm 142 into theposition shown, where fluid communication between intermediate pressurechamber 130 and outlet 148 (comprising 148 a, 148 b, and 148 c) mayoccur at least at location 160. With servo valve 134 and servo valve 152both positioned as shown at FIG. 2C, this allows fluid communicationbetween inlet 122 and outlet 148, and may allow a fuel supply to proceedfrom inlet 122 to a main burner, such as main burner 42 (FIG. 1). Withfuel supplied to the main burner and the pilot flame established, a mainflame may be generated at the main burner.

Allowing servo valve 152 to close will return diaphragm 142 to theposition depicted in FIGS. 2A-2B, terminating the main fuel supply tothe main burner. Consequently, when servo valve 152 is an electricallyactuated valve requiring energization to remain open, such as a solenoidvalve, servo valve 152 receives electrical power throughout the periodmain burner operation is desired. As a result, excessive powerexpenditures can be avoided by periodically determining a sufficientlevel of power necessary to open and hold open servo valve 152 and thenapplying that level of power when main burner operation is called for.This may be particularly meaningful when a control system is wholly orpartially reliant on a limited power supply to supply all or a largeportion of the electric power needs required, including continuedenergization of servo valve 134 and servo valve 152 when main burneroperation is called for. Providing an efficient amount of electric powerto servo valves 134 and 152 may increase the availability of electricalpower to other powered components in water heating system 70 (FIG. 2).

An example water heater control system 10 which may be configured toprovide electrical power to one or more control valves is depicted atFIG. 3. Control system 10 may be configured operate a first controlvalve, such as servo valve 134 (FIG. 2A-2C), to cause a pilot gas flowto issue from a pilot burner. System 10 may also be configured tooperate a second control valve, such as servo valve 152 (FIGS. 2A-2C),configured to cause a main gas flow to issue from a main burner. Eachvalve may be operated via electrical power provided to a specific valveoperator. For example, each control valve may be a solenoid operatedvalve comprising a solenoid, and the solenoid may be the specific valveoperator energized by system 10.

System 10 is an electric circuit configured to receive power from athermoelectric device 16. Thermoelectric device 16 is a componentconfigured to convert thermal energy into electrical power, such as athermopile. In examples, thermoelectric device 16 may be the sole sourceof electrical energy to system 10 and the components within system 10,or system 10 may additionally comprise rechargeable or non-rechargeablebatteries and/or capacitors. Thermoelectric device 66 of FIG. 1 is anexample thermoelectric device 16. System 10 additionally comprises pilotvalve operator 12 and main valve operator 14, as well as convertor 18.Pilot valve operator 12 may be configured to actuate a pilot valve suchas the pilot valve of system 70 (FIG. 1), and main valve operator 14 maybe configured to actuate a main valve such as main valve 44 (FIG. 1).

As illustrated, thermoelectric device 16 may provide power to main valveoperator 14 through electrical line 34, and to convertor 18 throughelectrical connection 36. Convertor 18 may forward the generated powerthrough electrical line 39 to energy storage system 20 throughelectrical connection 40, and to pilot valve operator 12 throughelectrical connection 38. Energy storage system 20 may also providepower to pilot valve operator 12 through electrical connection 40 andelectrical connection 38. Energy storage system 20 thus provides thecapability to store some portion of the electrical power generated bythermoelectric device 16, and also provides for powering of pilot valveoperator 12 when thermoelectric device 16 is not generating. Forexample, thermoelectric device 16 may be configured to be in thermalcommunication with a heat source intended to operate intermittently,such as an intermittent pilot flame in a water heater. Energy storagesystem 20 may also power an ignition circuit 24. System 10 may furthercomprise a microcontroller 22 configured to receive power throughelectrical connection 37 from either convertor 18 or energy storagesystem 20. In the example illustrated at FIG. 3, Microcontroller 22 isshown as configured to receive power through electrical connection 37from either convertor 18 or energy storage system 20. However,microcontroller 22 may be additionally or exclusively powered from apower source such as a battery or capacitor. The battery may be anon-rechargeable battery or pre-charged capacitor having a life thatlasts as long as a life of the water heater device.

Additionally, system 10 may be configured to limit power flow from node35 to energy storage system 20 to a single direction using, for example,converter 18 or another electronic device, so that while energy storagesystem 20 may receive power from thermoelectric device 16 through node35, power flow cannot occur from energy storage system 20 to anycomponents where node 35 is in the electrical path, such as main valveoperator 14. This configuration may be employed so that main valveoperator 14 can only receive power when thermoelectric device 16 isgenerating power, whereas pilot valve operator 12 may receive power fromthermoelectric device 16 via converter 18 (when thermoelectric device 16is generating) or energy storage system 20 (when thermoelectric device16 is not generating). This configuration of system 10 may be providedto ensure a pilot flame is present at a pilot burner prior toestablishing a main gas flow to a main burner.

System 10 may comprise microcontroller 22. In examples, microcontroller22 is configured to establish and terminate electrical contact betweenthermoelectric device 16 and pilot valve operator 12 using, for example,a first electronic device 26. Microcontroller 22 may be is configured toestablish and terminate electrical contact between thermoelectric device16 and main valve operator 14 using, for example, a second electronicdevice 28. Microcontroller 22 may also be configured to establish andterminate electrical contact between convertor 18 and energy storagesystem 20 using, for example, a third electronic device 30.Microcontroller 22 may also be configured to establish and terminateelectrical contact between pilot valve operator 12 and energy storagesystem 20 using second electronic device 26 and third electronic device30. First electronic device 26, second electronic device 28, and thirdelectronic device 30 may each be an apparatus sufficient to establishand terminate electrical contact between two portions of an electricalsystem in response to a signal from microcontroller 22. For example,first electronic device 26, second electronic device 28, and/or thirdelectronic device 30 may comprise a field effect transistor (FET), arelay, a separate switching circuit, or any other device capable ofestablishing and terminating electrical contact in response to a signalfrom microcontroller 22.

System 10 may control an intermittent pilot water heating system or awater system in which the pilot is always lit and operate in the absenceof an externally provided power supply. Under such conditions, when mainburner operation is called for, pilot valve operator 12 may bede-energized and fuel flow through the pilot valve blocked, such thatthe pilot flame is dormant. With the pilot flame dormant, system 10 mayinitiate establishment of the dormant pilot flame by energizing pilotvalve operator 12 using stored energy system 20, initiating a pilot gasflow to a pilot burner such as pilot burner 41 (FIG. 1). Similarly,system 10 may energize ignition circuit 24 to cause pilot spark ignitor32 to generate thermal energy. Similar to pilot burner 41 and pilotspark ignitor 56 of FIG. 1, pilot spark ignitor 32 may be in thermalcommunication with the pilot gas flow such that the pilot flamegenerates. With thermoelectric device 16 in thermal communication withthe established pilot flame, thermoelectric device 16 generateselectrical energy from the thermal energy of the pilot flame andprovides this electrical energy to main valve operator 14. Main valveoperator 14 may actuate a main valve such as main valve 44 (FIG. 1),providing a main fuel flow to a main burner such as main burner 48 (FIG.1). The established pilot flame is in thermal communication with themain fuel flow and generates combustion of the main fuel flow.

In between periods where a main burner flame is requested,microcontroller 22 of system 10 may be additionally configured toperiodically wake and check the status of energy storage system 20. Thisensures that energy storage system 20 has sufficient stored energy toinitiate the pilot flame sequence described above when necessary. Ifenergy storage system 20 is below a threshold level of charge,microcontroller 22 may be configured to energize pilot valve operator 12using stored energy system 20, and/or may be configured to initiate thepilot gas flow, energize ignition circuit 24, and cause establishment ofthe pilot flame and generation of electrical energy from thermoelectricdevice 16. Microcontroller 22 may be configured to provide theelectrical energy generated by thermoelectric device 16 to stored energysystem 20, in order to recharge stored energy system 20.

A control system such as system 10 may benefit from microcontroller 22being configured to periodically determine one or more electricalparameters required to maintain a control valve in an open position, andthen subsequently apply the one or more electrical parameters whencontrol valve operation is required. As discussed, the electrical powersufficient to maintain a given control valve open may increase and/ordecrease over the life and continued operation of the control valve dueto mechanical wear, changes in environmental conditions, or otherreasons. In a system such as system 10—which relies on either athermoelectric device generating electrical power, or an energy storagesystem providing electrical power previously generated by thethermoelectric device—periodic evaluation and subsequent application ofthe sufficient power level for opening and holding open a specificcontrol valve can mitigate excessive expenditures of the limited poweravailable. Additionally, periodically determining and subsequentlyproviding the sufficient levels of power may increase the availabilityof electrical power for other powered components either within thecontrol system or elsewhere in a water heating system, as opposed touniformly applying predetermined power levels throughout the life of acontrol valve.

As an example, FIG. 4 illustrates a system 80 suitable for use within awater heating system such as water heating system 70 (FIG. 1). As willbe discussed, system 80 may be incorporated within or present in a waterheater control system such as system 10 (FIG. 3). System 80 comprises amicroprocessor 82 configured to receive power from thermoelectric device88. In FIG. 4, microprocessor 82 is configured to receive power fromthermoelectric device 88 via electrical lead 81 and electricalconnection 83. Thermoelectric device 88 is configured to generateelectrical energy by converting thermal energy from a flame 92. Flame 92is sustained by a gas flow 91 flowing into burner 93. Thermoelectricdevice 88 may be, for example, thermoelectric device 16 (FIG. 3) orthermoelectric device 66 (FIG. 1). Microprocessor 82 may bemicroprocessor 22 (FIG. 3). Gas flow 91 may be, for example, a pilot gasflow flowing into pilot burner 41.

System 80 further includes valve operator 84 within valve 87. Valveoperator 84 is configured to establish a position of valve 87. Valveoperator 84 might be, for example, pilot valve operator 12 or main valveoperator 14 (FIG. 3). Valve 87 is configured to control whether or not agas flow is present to cause a flame, based for example on a position ofdisc 90. Valve 87 might be, for example, servo valve 134 configured tocontrol whether a pilot gas flow issues from pilot outlet 132, or servovalve 152 configured to control whether a main gas flow issues fromoutlet 156 (FIGS. 2A-2C).

Microcontroller 82 is configured to provide or facilitate some portionof a voltage present at node 94 to power valve operator 84. For example,microcontroller 84 may be configured to utilize electronic device 86 toprovide some portion of the voltage at node 94 to valve operator 84.Electronic device 86 may be an apparatus sufficient to establish andterminate electrical contact between valve operator 84 and node 94,among other functions. For example, electronic device 86 may be acircuit comprising a Pulse Width Modulator (PWM) controlling a FieldEffect Transistor (FET), and microcontroller 84 may be configured todetermine the switching rate and/or pulse period of the PWM. The FET maybe in series with valve operator 84 and node 94, and the PWM may beconfigured to cause the FET to rapidly open and close, to provide anaverage voltage and average current to valve operator 84 determined by,for example, a ratio of the FET on-time to a pulse period determined bythe PWM.

Microcontroller 82 is configured to provide or facilitate one or moreelectrical parameters to valve operator 84 and cause sufficient currentto flow through valve operator 84 to establish and hold valve 87 in anopen state. For example, when valve 84 is a solenoid valve comprising asolenoid and a plunger and valve operator 84 is the solenoid,microcontroller 82 may provide one or more electrical parameters tovalve operator 84 to initially generate a pick current to bring theplunger to an open state, followed by a generally lower hold current tomaintain the plunger in the open state. Microcontroller 82 is furtherconfigured periodically determine one or more electrical parameters forholding valve 87 in the open state, based at least in part oninformation indicative of whether the valve is in the open state.

For example, when valve 87 is a solenoid valve comprising a solenoid anda plunger and valve operator 84 is the solenoid, microcontroller 82 maybe configured to alter the one or more electrical parameters provided tovalve operator 84 in a manner that causes a decrease in the currentthrough the solenoid from a holding current to a drop current.Microcontroller 82 may then revise the one or more electrical parametersfor holding valve 87 in the open state based on the quantity of the oneor more parameters which resulted in the drop current.

In other words, microcontroller 82 may first open valve 87, and thenkeep reducing the current that flows through valve operator 84 (e.g.,modify the duty cycle of the PWM to reduce the current that flowsthrough valve operator 84). Microcontroller 82 may keep reducing thecurrent until valve 87 closes (or deviates from the open state). Thecurrent at which valve 87 closes is the drop current. Microcontroller 82may determine the electrical parameters that generated the current levelright before the drop current level as microcontroller 82 was reducingthe current flowing through valve operator 84. Microcontroller 82 maythen cause the determined electrical parameters to be applied to valve87 the next time valve 87 is to remain open (e.g., microcontroller 82may first apply a pick current to cause valve 87 to transition to anopen state and then apply the determined electrical parameters to keepvalve 87 in the open state). Microcontroller 82 may periodically performsuch operations to determine the minimum current needed to keep valve 87in an open state (e.g., determine the hold current) and deliver currentat or approximately at the hold current (e.g., up to 20% above the dropcurrent).

As described above, part of the technique in which microcontroller 82determines the hold current and the drop current is based on informationindicative of whether valve 87 is in an open state or a closed state(e.g., if valve 87 has deviated from an open state). Microcontroller 82may be configured to discern the indicative information evidencing thatvalve 87 has experienced the drop current and deviated from an openstate (e.g., transitioned from an open position to a generally closedposition) through a variety of methods, including a change in the amountof electrical energy received from thermoelectric device 88, or avoltage signature, current signature, or inductive signature of valveoperator 84.

Having revised the one or more electrical parameters based on thequantity of the one or more parameters which resulted in the dropcurrent, and having thereby determined one or more electrical parametersfor holding valve 87 in the open state, microcontroller 82 is configuredto cause a current to flow through valve operator 84 based on thedetermined one or more parameters. This capability allows microprocessor84 to adjust the electrical power provided to hold open valve operator84 as the electrical power requirements change over the operatinglifetime of valve operator 84 within system 80. The periodic evaluationand subsequent application of the electrical power level for holdingopen valve 87 can mitigate excessive expenditures of the limited powerwhich may be available to system 80.

A controller such as microcontroller 82 can offer significant advantagewhen utilized in a system such as system 10 (FIG. 3), where the periodicoperation of power pilot operator 12, main valve operator 14,microcontroller 22, converter 18, ignition circuit 24, and pilot sparkignitor 32 may be wholly reliant on electrical power either directlygenerated by thermoelectric device 16, or generated by thermoelectricdevice 16 and stored by energy storage system 20. Reducing theelectrical energy provided to pilot valve operator 12 to hold open, forexample, pilot servo valve 134, and reducing the electrical energyprovided to main valve operator 14 to hold open, for example, main servovalve 152, may decrease the overall electrical energy expenditurerequired to initiate and maintain pilot and main burner flames whenrequired. This reduction may decrease the amount of stored energywithdrawn from energy storage system 20 during the period when pilotvalve operator 12 is energized but thermoelectric device 16 is not yetgenerating electrical energy. This reduction may also decrease theportion of the electrical energy generated by thermoelectric device 16which must be dedicated to energizing pilot valve operator 12 and mainvalve operator 14, thereby increasing the energy budget which might beallocated to other components present in the water heating system.

The one or more electrical parameters required to hold valve 87 in anopen state may include a voltage provided to valve operator 84, withmicroprocessor 82 is configured to cause a current to flow through valveoperator 84 based on the voltage. The one or more electrical parametersrequired to hold valve 87 in an open state may include a currentprovided to valve operator 84, with microprocessor 82 is configured tocause the current to flow through valve operator 84. Microprocessor 82is configured to cause a current to flow through valve operator 84 basedon the determined one or more electrical parameters. In examples,microprocessor 82 is configured to determine a holding amount of the oneor more electrical parameters for holding valve 87 in an open positionby establishing valve 87 in an open position, confirming valve 87 is inthe open position, then altering the one or more electrical parametersprovided and determining when valve 87 deviates from the open position.

Microcontroller 82 may determine when valve 87 is in an open state usingany suitable technique. In an example, microcontroller 82 determinesthat valve 87 is in an open state based on reception of an increase inthe amount of electrical energy generated by thermoelectric device 91.As discussed, valve 87 may be configured to control whether or not gasflow 91 sustaining flame 92 is present, and thermoelectric device 88 isconfigured to generate electrical energy by converting thermal energyfrom a flame 92. Consequently, microprocessor 82 may conclude that valve87 is in an open position based on an increase in the electrical energyreceived from thermoelectric device 88. Microprocessor 82 may alsoconclude that valve 87 has closed or deviated from the open state basedon a decrease in the electrical energy received from thermoelectricdevice 88. Correspondingly, microprocessor 82 may be configured todiscern information indicative of whether valve 87 is in the open statebased at least in part on the electrical energy received fromthermoelectric device 88, and may be configured to determine that valve87 has deviated from the open state (e.g. Closed) based at least in parton the electrical energy received from thermoelectric device 88.

The increase in the electrical energy is generally due to the pilotflame, which means that the pilot gas is allowed to flow, which meansthat valve 87 is open. Conversely, when valve 87 is closed, gas flow 91is not present and the pilot light extinguishes, causing the voltagefrom thermoelectric device 88 to be substantially lowered (e.g., closeto or equal to zero). Accordingly, as microcontroller 82 reduces thecurrent to determine the minimum current needed to keep valve 87 open,once microcontroller 82 reduces the current to the drop current, valve87 may close and thermopile 88 may stop generating a voltage.Microcontroller 82 may utilize this sudden drop in the voltage fromthermopile 88 as indicative of gas flow 91 shutting off, indicating thatvalve 87 is substantially closed, and indicating that microcontroller 82has reduced the current through valve 87 to the drop current of valve87.

Additionally, and as will be discussed, in some examples microprocessor82 may conclude that valve 87 is in an open position based on a decreasein the electrical energy received from thermoelectric device 88. Forinstance, in examples where valve 87 is for a main burner, the pilotvalve is already open and a pilot flame may be lit. In such examples,gas flow 91 is for the main burner. When valve 87 is open, and gas flow91 flows to light the main burner, there may be a much stronger flame,which can cause thermoelectric device 88 to generate a lower voltage dueto an increase in an overall ambient temperature. Thermoelectric device88 generates a voltage based on a differential temperature across two ormore sensors. If the overall ambient temperature is high, due to arelatively strong flame from the main burner, then the differentialtemperature may be lower, and the voltage from thermoelectric device 88may be lower. Accordingly, when valve 87 controls the gas flow for themain burner, a decrease in voltage from thermoelectric device 88 may beindicative of valve 87 being open. Conversely, when the main burnerflame extinguishes, the voltage from thermoelectric device 88 mayincrease, indicating valve 87 has closed (or deviated from the openstate). Therefore, by determining whether the voltage fromthermoelectric device 88 increased or decreased, microcontroller 82 maydetermine whether a valve (e.g., valve 87) has deviated from the openstate.

In some examples, microcontroller 82 might discern informationindicative of whether valve 87 is in an open state based on a voltagesupplied to valve operator 84. In some examples, microcontroller 82might discern information indicative of whether valve 87 is in an openstate based on a current supplied to valve operator 84. In someexamples, microcontroller 82 might discern information indicative ofwhether valve 87 is in an open state based on an inductive signal ofvalve operator 84.

For example, when valve 87 is a solenoid valve comprising a plunger andvalve operator 84 is a coil influencing a position of the plunger, thevalve operator 84 would be expected to define a performance curvebetween a first state when an air gap between the coil and plunger is ata maximum (air gap open (AGO)) and a second state when the air gapbetween the coil and plunger is at a minimum (air gap closed(AGC)). Theperformance curve may have particular voltage, current, and/or inductivesignature markers indicating when the AGO and AGC positions occur or arebeing approached. The marker may be, for example, a certain increase ordecrease of the voltage, current, and/or inductive signature, or may bethe attainment of a specific value of the voltage, current, and/orinductive signature. Microprocessor 82 may be configured to recognizeone or more of these markers associated with the AGO and AGC positions,and determine when valve 87 is in an open state based on the markerrecognized. Correspondingly, microprocessor 82 may be configured todiscern information indicative of whether valve 87 is in the open statebased at least in part on an observed increase or decrease of thevoltage, current, and/or inductive signature, or recognition of anevident voltage, current, and/or inductive signature marker.Microprocessor 82 may also be configured to determine that valve 87 hasdeviated from the open state (e.g. Closed) based at least in part on arecognized increase or decrease of the voltage, current, and/orinductive signature, or recognition of a distinct voltage, current,and/or inductive signature marker.

In an example, microcontroller 82 periodically determines the one ormore electrical parameters for holding valve 87 in the open state byinitially causing valve 87 to assume and hold an open position.Microprocessor 82 may be configured to accomplish this by initiallyproviding a picking amount of the one or more electrical parameters tocause a pick current to flow to valve operator 84 to open valve 87,followed by providing a holding amount of the one or more electricalparameters to cause a hold current to flow to valve operator 84 to holdopen valve 87. The picking amount and the holding amount initiallyprovided may be based on one or more of a previous evaluation of theelectrical parameters necessary to open and maintain valve 87 in an openstate, predetermined test levels of the picking amount and holdingamount, and the picking and holding amounts the controller is presentlyconfigured to provide at the commencement of the periodic determination.

With valve 87 established in the open state, microcontroller 82evaluates the holding amount by decreasing the one or more electricalparameters until valve 87 deviates from the open position. In anexample, microcontroller 82 is configured to decrease the one or moreelectrical parameters utilizing electronic device 86. Electronic device86 may be configured to decreases the one or more electrical parametersbased on direction from microprocessor 82.

For example and as discussed, electronic device 86 may be a circuitcomprising a PWM controlling a FET. The FET may be in series with valveoperator 84 and node 94, and the PWM may be configured to cause the FETto rapidly open and close in order to provide an average voltage andaverage current to valve operator 84. Microcontroller 82 may beconfigured to control the duty cycle (e.g., pulse period) of the PWM,and may decreases the one or more electrical parameters by altering theswitching rate and/or pulse period. Other techniques may be utilized.For example, microcontroller 82 may be configured to control apotentiometer using some portion of the voltage at node 94 as an inputvoltage and supplying an output voltage to valve operator 84. Thepotentiometer may be a digital potentiometer. Microcontroller 82 may beconfigured to control an electronic circuit comprising one or more of anop-amp, a transistor, and/or a diode, with the electronic circuitconfigured within system 80 to provide a voltage to valve operator 84.In some examples, microcontroller 82 may be configured to control anindependent or dependent current source configured within system 80 toprovide a current to the coil of valve operator 84. The current sourcemay be an electronic circuit comprising an op-amp, a transistor, and/ora diode. Microcontroller 82 may be configured to control a rheostatconfigured within system 80 to provide a current to the coil of valveoperator 84.

As used herein, “holding amount” means a voltage, a current, or avoltage and a current provided to a valve in order to maintain the valvein an open state. In an example, the voltage, current, or voltage andcurrent is provided to a valve operator for the valve. The valve may bea solenoid valve comprising a solenoid as the valve operator, and thevoltage, current, or voltage and current may cause a holding current toflow through the solenoid.

As used herein, “picking amount” means a voltage, a current, or avoltage and a current provided to an actuated valve (e.g., a valve in ade-actuated state) in order to transition the valve from a closed stateto an open state. In an example, the voltage, current, or voltage andcurrent is provided to a valve operator for the valve. The valve may bea solenoid valve comprising a solenoid as the valve operator, and thevoltage, current, or voltage and current may cause a pick current toflow through the solenoid.

As used herein, “dropping amount” means a voltage, a current, or avoltage and a current provided to a valve which is insufficient tomaintain the valve in an open state. The dropping amount may cause thevalve to transition from an open state to a closed state. In an example,the voltage, current, or voltage and current is provided to a valveoperator for the valve. The valve may be a solenoid valve comprising asolenoid as the valve operator, and the voltage, current, or voltage andcurrent may cause a drop current to flow through the solenoid.

As used herein, a valve in an open state means a valve where amicroprocessor such has microprocessor 82 has discerned that the valveis in the open state using one or more indications, such as an increaseor decrease in electrical energy received from a thermoelectric device,an observed increase or decrease of the voltage, current, and/orinductive signature of the valve or a valve operator, and/or an evidentvoltage, current, and/or inductive signature marker of the valve orvalve operator.

As used herein, a valve in a closed state or a valve which has deviatedfrom an open state means a valve where a microprocessor such asmicroprocessor 82 has discerned that the valve is in the closed state orhas deviated from the open state using one or more indications, such asan increase or decrease in electrical energy received from athermoelectric device, a recognized increase or decrease of the voltage,current, and/or inductive signature of the valve or a valve operator,and/or recognition of a distinct voltage, current, and/or inductivesignature marker of the valve or valve operator.

Microcontroller 82 may be configured to determine when valve 87 deviatesfrom an open position using a variety of suitable techniques. Forexample, microcontroller 82 may be configured to determine when valve 87deviates from an open position based on an increase or decrease in theelectrical energy received from thermoelectric device 88. In examples,microcontroller 82 may be configured to determine when valve 87 deviatesfrom an open position based on changes to the voltage, current, and/orinductive signature markers of valve operator 84. In this manner,microcontroller may determine a dropping amount of the one or moreparameters, where the dropping amount is the amount provided to valveoperator 84 when microcontroller 82 determines that valve 87 hasdeviated from an open position.

Microcontroller 82 may be configured to then revise the holding amountof the one or more electrical parameters provided to valve operator 84based on the dropping amount of the one or more electrical parameters.For example, microcontroller 82 may revise the holding amount of the oneor more electrical parameters by adding a margin to the dropping amountof the one or more electrical parameters. In this manner, microprocessor84 may recognize when the electrical power required to maintain valve 87in the open position has decreased due to mechanical wear, changes inenvironmental conditions, or some other reason, and subsequently applythe revised one or more electrical parameters. Periodic determination ofthe electrical parameters necessary to hold open specific control valvesmitigates excess expenditures of electrical power, and can providesignificant advantage in the operations of systems where available powermay be limited. This can be particularly beneficial in water heatercontrol systems which rely on a stored energy system or a thermoelectricdevice to supply operating power, rather than power from a line sourceexternal to the water heater. For example, the periodic determination ofelectrical parameters may be particularly beneficial in a system such aswater heater system 70 (FIG. 1) controlled by control system 10 (FIG.3), where energy storage system 20 may be expected to provide power fora variety of functions when thermoelectric device 16 (or thermoelectricdevice 41 of FIG. 2) is not providing appreciable electrical power.

In some examples, microcontroller 82 is configured to receive atemperature signal T_(ENV) indicative of the environmental temperatureconditions of valve operator 84 and associate the determined parameterswith the temperature signal T_(ENV). For example, when valve operator 84is located within control system 71, microcontroller 82 may beconfigured to receive a temperature signal T_(ENV) indicative of theenvironmental temperature conditions of control system 71 (e.g., atemperature within control housing 72). In some examples, control system71 includes a temperature sensor configured to determine a temperatureindicative of the environmental temperature (e.g., a temperature sensorwithin control housing 71) and provide the temperature signal T_(ENV) tomicrocontroller 82. In some examples, a water heating system comprises atemperature sensor such as temperature sensing device 62 (FIG. 1)configured to provide a signal T_(REF), and the temperature signalT_(ENV) is based on a signal T_(REF) indicative of a temperature fromthe temperature sensor.

Microcontroller 82 may associate the determined parameters with thetemperature signal T_(ENV) when periodically determining the one or moreparameters. Over time, microcontroller 82 may determine a plurality ofdata sets, with each data set comprising a particular temperature signalT_(ENV) or other temperature signal and, for example, a holding amountof the one or more electrical parameters required to hold open valve 87at the particular temperature signal T_(ENV). Subsequently, when valve87 operation is required, microcontroller 82 may receive the temperaturesignal T_(ENV) providing a possible indication of the currenttemperature conditions of valve operator 84, and cause current to flowthrough valve operator 84 using the plurality of data sets and based onthe temperature signal T_(ENV) in the plurality of data sets. This maybe advantageous when valve operator 84 is potentially subject to avariety of environmental temperatures and the varying environmentaltemperatures impact the electrical properties of valve operator 84. Forexample, valve operator 84 may be subject to varying environmentaltemperatures as a result of changing seasons, or due to a proximity toother appliances or devices which generate heat on a periodic basis, orsome other reason.

In examples, valve 87 of FIG. 4 is a valve configured to provide a pilotgas flow to cause a pilot flame. For example, valve 87 may be servovalve 134 (FIGS. 2A-2C) configured to control whether a pilot gas flowissues from pilot outlet 132 to pilot burner 41 of water heater system70 (FIG. 1). Valve operator 84 (FIG. 4) may be a valve operatorcontrolling servo valve 134, such as pilot valve operator 12 (FIG. 3).Electronic component 86 (FIG. 4) may be a component controlling avoltage and current provided to pilot valve operator 12, such as firstelectronic component 26 (FIG. 3). Microprocessor 82 may bemicroprocessor 22 of FIG. 3, configured to establish and terminateelectrical contact between thermoelectric device 16 and pilot valveoperator 12 using first electronic device 26, as well as to periodicallydetermine the one or more electrical parameters sufficient to hold openservo valve 134 using pilot valve operator 12. Microcontroller 22 may beconfigured to control one or more electrical parameters provided topilot valve operator 12 using first electronic device 26. For example,first electronic device 26 may be a circuit comprising a Pulse WidthModulator (PWM) controlling a Field Effect Transistor (FET), andmicrocontroller 22 may be configured to determine the switching rateand/or pulse period of the PWM to provide an average voltage and averagecurrent to pilot valve operator 12. Microcontroller 22 may be configuredto determine a holding amount of the one or more parameters for pilotvalve operator 12 and servo valve 134 in like manner to the techniqueemployed by microprocessor 82 for valve operator 84 and valve 87.

In some examples, valve 87 of FIG. 4 is a valve configured to provide amain gas flow to cause a main burner flame. For example, valve 87 may beservo valve 152 (FIGS. 2A-2C) configured to control whether a main gasflow issues from outlet 156 to main burner 42 of water heater system 70(FIG. 1). Valve operator 84 (FIG. 4) may be a valve operator controllingservo valve 152, such as main valve operator 14 (FIG. 3). Electroniccomponent 86 (FIG. 4) may be a component controlling a voltage andcurrent provided to main valve operator 14, such as second electroniccomponent 28 (FIG. 3). Microprocessor 82 may be microprocessor 22 ofFIG. 3 configured to establish and terminate electrical contact betweenthermoelectric device 16 and main valve operator 14 using secondelectronic device 28, as well as to periodically determine the one ormore electrical parameters sufficient to hold open servo valve 152 usingmain valve operator 14. Microcontroller 22 may be configured to controlone or more electrical parameters provided to main valve operator 14using second electronic device 28. For example, second electronic device28 may be a circuit comprising a Pulse Width Modulator (PWM) controllinga Field Effect Transistor (FET), and microcontroller 22 may beconfigured to determine the duty cycle (e.g., pulse period) of the PWMto provide an average voltage and average current to main valve operator14. Microcontroller 22 may be configured to determine a holding amountof the one or more parameters for main valve operator 14 and servo valve152 in like manner to the technique employed by microprocessor 82 forvalve operator 84 and valve 87.

In some examples, the configuration between microcontroller 82 and valveoperator 84 illustrated in FIG. 4 may be present between amicrocontroller and more than one valve operator. For example, in FIG.3, microcontroller 22 may be configured to establish and terminateelectrical contact between thermoelectric device 16 and pilot valveoperator 12 using first electronic device 26, and establish andterminate electrical contact between thermoelectric device 16 and mainvalve operator 14 using second electronic device 28. Further, firstelectronic device 26 may be configured to decrease one or moreelectrical parameters to pilot valve operator 12 based on direction frommicroprocessor 22, and second electronic device 28 may be configured todecrease one or more electrical parameters to main valve operator 14based on direction from microprocessor 22. First electronic device 26and second electronic device 28 may each be a circuit comprising a PWMcontrolling a FET, and microcontroller 22 may be configured to determinethe switching rate and/or pulse period of the PWM of each circuit toprovide a first average voltage and first average current to pilot valveoperator 12, and a second average voltage and second average current tomain valve operator 14. Microcontroller 22 may be configured todetermine a holding amount of the one or more parameters for pilot valveoperator 12 and servo valve 134 in like manner to the technique employedby microprocessor 82 for valve operator 84 and valve 87, as well as beconfigured to determine a holding amount of the one or more parametersfor main valve operator 14 and servo valve 152 in like manner to thetechnique employed by microprocessor 82 for valve operator 84 and valve87.

An example technique a controller may perform to periodically determineone or more electrical parameters for holding a valve might compriseproviding a sufficient amount of the one or more electrical parametersfor holding the valve in an open state. The sufficient amount may bebased on a holding amount previously determined by the controller. Thesufficient amount of the one or more electrical parameters may include avoltage and may include a current. The controller may cause a current toflow through valve operator based on one or more electrical parameters.The controller may receive a signal indicative of a temperature T_(REF).

After providing the sufficient amount of the one or more electricalparameters, the controller may determine that the valve is open. Thecontroller may determine the valve is open based on an amount ofelectrical energy generated by a thermoelectric device. The controllermay determine when the valve is open based on a voltage supplied to avalve operator establishing a position of the valve. The controller maydetermine when the valve is open based on a current supplied to a valveoperator. The controller may determine the valve is open based on aninductive signal of the valve operator.

With the valve in the open state, the controller may decrease the one ormore electrical parameters. The controller may decrease a voltage andcause current to flow through the valve operator based on the reducedvoltage. The controller may reduce a current and cause the reducedcurrent to flow through the valve operator. The controller may determinewhether the valve has deviated from the open state. The controller maydetermine whether the valve has deviated from the open state based on anincrease or decrease in the amount of electrical energy received fromthe thermoelectric device. The controller may determine whether thevalve has deviated from the open state based on changes to the voltage,current, and/or inductive signature markers of a valve operatorestablishing a position of the valve.

If the valve has not deviated from the open state, the controller mayrepeat decreasing the one or more electrical parameters and determiningif the valve has deviated from the open state. If the valve has deviatedfrom the open state, the controller may designate the one or moreelectrical parameters currently supplied to the valve operator as thedropping amount, and revise the holding amount of electrical power basedon the dropping amount. For example, controller may revise thesufficient amount of the one or more electrical parameters by adding apredetermined margin to the dropping amount of the one or moreelectrical parameters which resulted in the deviation of the valve fromthe open state. The controller may associate the revised holding amountof the one or more electrical parameters with the signal indicative of atemperature T_(REF).

A controller such as microcontroller 82 configured to periodicallyestablish and revise the one or more electrical parameters required tomaintain a specific control valve in an open position may providedistinct advantage when utilized in a system such as system 10 (FIG. 3),where power pilot operator 12, main valve operator 14, microcontroller22, converter 18, ignition circuit 24, and pilot spark ignitor 32 may bewholly reliant on electrical power provided directly or indirectly bythermoelectric device 16. Reducing the required electrical energy whichmust be provided to pilot valve operator 12 and main valve operator 14may decrease the overall electrical energy expenditure required toinitiate and maintain pilot and main burner flames when required, andincrease the energy budget which might be allocated to other componentspresent in the water heating system.

In some examples, microcontroller 22 (FIG. 3) is configured in likemanner to microcontroller 88, and may periodically determine the one ormore electrical parameters sufficient to hold open servo valve 134 usingpilot valve operator 12 (i.e., the holding amount for pilot valveoperator 12). Microcontroller 22 may be configured to utilize firstelectronic component 26 to control a voltage and/or current provided topilot valve operator 12. Microcontroller 22 may be configured todetermine when servo valve 134 is open and when servo valve 134 deviatesfrom an open position based on, for example, an amount of electricalenergy generated by thermoelectric device 16 (or thermoelectric device66 of FIG. 1), a voltage supplied to pilot valve operator 12, a currentsupplied to pilot valve operator 12, and/or an inductive signal of pilotvalve operator 12. Microcontroller 22 may be configured to revise theholding amount of the one or more electrical parameters provided topilot valve operator 12 based on the periodic determination. Inexamples, microcontroller 22 may be configured to associate the revisedholding amount of the one or more electrical parameters with atemperature signal T_(REF) from a temperature sensor such as temperaturesensor 62 (FIG. 1). In examples, microcontroller 22 provides a holdingamount of the one or more electrical parameters to pilot valve operator12 based on comparison of a temperature T_(ENV) received and a T_(REF)value.

Microcontroller 22 (FIG. 3) may be further configured to periodicallydetermine the one or more electrical parameters sufficient to hold openservo valve 152 using main valve operator 14 (i.e., the holding amountfor main valve operator 14). Microcontroller 22 may be configured toutilize second electronic component 28 to control a voltage and/orcurrent provided to main valve operator 14. Microcontroller 22 may beconfigured to determine when servo valve 152 is open and when servovalve 152 deviates from an open position based on, for example, anamount of electrical energy generated by thermoelectric device 16 (orthermoelectric device 66 of FIG. 1), a voltage supplied to main valveoperator 14, a current supplied to main valve operator 14, and/or aninductive signal of main valve operator 16. Microcontroller 22 may beconfigured to revise the holding amount of the one or more electricalparameters provided to main valve operator 14 based on the periodicdetermination. In examples, microcontroller 22 may be configured toassociate the revised holding amount of the one or more electricalparameters with a temperature signal T_(REF) from a temperature sensorsuch as temperature sensor 62 (FIG. 1). In examples, microcontroller 22provides a holding amount of the one or more electrical parameters tomain valve operator 14 based on comparison of a temperature T_(ENV)received and a T_(REF) value.

In some examples, when microprocessor 22 is configured to periodicallydetermine holding amounts of the one or more electrical parameters forboth pilot valve operator 12 and main valve operator 14, microprocessor22 may determine that a valve operated by pilot valve operator 12 is inan open state based on an increase in the electrical energy receivedfrom thermoelectric device 16, and determine that a valve operated bypilot valve operator 14 is in an open state based on a decrease in theelectrical energy received from thermoelectric device 16. Similarly,microprocessor 22 may determine that a valve operated by pilot valveoperator 12 has closed or deviated from the open state based on andecrease in the electrical energy received from thermoelectric device16, and determine that a valve operated by pilot valve operator 14 hasclosed or deviated from an open state based on an increase in theelectrical energy received from thermoelectric device 16. Ifthermoelectric device 16 is a device generating electrical power basedon a temperature difference between a cold junction and a hot junction,the location of thermoelectric device 16 within a water heating systemmight result in a pilot flame alone causing a first temperaturedifference, while the pilot flame in conjunction with a main burnerflame (typically much larger) results in a second temperature differencedistinct from the first temperature difference. This may result when themain burner flame exerts a greater thermal influence on the generalenvironment surrounding the hot and cold junctions of thermoelectricdevice 16 as compared to a pilot flame alone. In this scenario, thegreater thermal influence of the main burner flame may act to increasethe temperature of one or both of the hot and cold junctions as comparedto the pilot flame acting alone, This may reduce the temperaturedifference between the hot and cold junctions, and reduce the amount ofelectrical energy produced by thermoelectric device 16 (orthermoelectric device 66 of FIG. 1).

For example, microprocessor 22 may interpret an increase in electricalenergy received from thermoelectric device 16 to a level substantiallyequal to the first amount of electrical energy to indicate a valve suchas servo valve 134 (FIG. 2A-2C) has opened and prompted generation of apilot flame. Microprocessor 22 may interpret a decrease in electricalenergy received from thermoelectric device 16 to a level less thansubstantially equal to the first amount to indicate a valve such asservo valve 134 (FIG. 2A-2C) has closed or deviated from the open state,and extinguished the pilot flame. In like manner, microprocessor 22 mayinterpret an decrease in electrical energy received from thermoelectricdevice 16 from a level substantially equal to the first amount to alevel substantially equal to the second amount to indicate a valve suchas servo valve 152 (FIG. 2A-2C) has opened and prompted generation of amain burner flame. Microprocessor 22 may interpret an increase inelectrical energy received from thermoelectric device 16 from a levelsubstantially equal to the second amount to a level substantially equalto the first amount to indicate a valve such as servo valve 154 (FIG.2A-2C) has closed or deviated from the open state, extinguishing themain burner flame.

In some examples, microprocessor 82 is configured to determine a pickingamount of the one or more electrical parameters required to bring acontrol valve to an open state from a closed state. For example and asdiscussed, when valve 84 is a solenoid valve comprising a solenoid and aplunger and valve operator 84 is the solenoid, microcontroller 82 mayinitially provide a picking amount of the one or more electricalparameters to valve operator 84, in order to establish a pick current inthe coils of operator 84 and bring the plunger to an open state.Microprocessor 82 may subsequently provide a holding amount of the oneof more electrical parameters, in order to establish a generally lowerhold current in the coils of operator 84 to maintain the plunger in theopen state. In some examples, microprocessor 82 may be configured toperiodically determine a picking amount required to establish a pickcurrent to flow through a valve operator. Microprocessor 82 may beconfigured to periodically determine the picking amount in addition toperiodically determining the holding amount for a valve operator.

An example technique a controller may perform to periodically determinea picking amount of the one or more electrical parameters might compriseproviding a picking amount of the one or more electrical parameterssufficient to transition the valve from a closed state to an open state.The picking amount may be based on a picking amount previouslydetermined by the controller. The picking amount of the one or moreelectrical parameters may include one or more of a voltage and acurrent. The controller may cause a current to flow through valveoperator based on the one or more electrical parameters. The controllermay receive a signal indicative of a temperature T_(REF).

After providing the picking amount of the one or more electricalparameters, the controller may determine that the valve is open. Thecontroller may determine the valve is open based on an amount ofelectrical energy generated by a thermoelectric device. The controllermay determine when the valve is open based on a voltage supplied to avalve operator establishing a position of the valve. The controller maydetermine when the valve is open based on a current supplied to a valveoperator. The controller may determine the valve is open based on aninductive signal of the valve operator.

If the controller verifies the valve is open, the controller may thenterminate providing electrical power to the valve, allowing the valve toclose. The controller may then revise the one or more electricalparameters of the picking amount. For example, the controller may revisethe one or more electrical parameters of the picking amount such that apick current provided to the valve decreases. The controller may thenrepeat the process as long as a verification indicates the valve isopen.

If the valve is not open, the controller may finalize the picking amountof the one or more electrical parameters. For example. The controllermay finalize the picking amount based on an amount of the one or moreelectrical parameters which produced an open verification. Thecontroller may finalize the picking amount based on the most recentamount of the one or more electrical parameters which produced an openverification. The controller may also finalize the picking amount of theone or more electrical parameters based on an amount of the one or moreelectrical parameters which produced a non-open state. For example, thecontroller may finalize the picking amount of the one or more electricalparameters based on the most recent one or more electrical parameterswhich produced a non-open state. The controller may associate thefinalize picking amount of the one or more electrical parameters withthe signal indicative of the temperature T_(REF).

An example technique for determining one or more electrical parametersto be delivered to a valve is illustrated at FIG. 5. The technique mayinclude generating electrical power using a thermoelectric deviceconverting thermal energy from a flame into electrical energy (422). Thetechnique may include delivering, using the controller, a quantity ofthe electrical power to a valve operator configured to hold a valve inan open state while receiving the quantity of electrical power (424).

The technique may further include monitoring, using the controller,whether the valve is in the open state (426). The technique may includemonitoring the open state using at least one of an amount of electricalpower received from the thermoelectric device, a voltage provided to thevalve operator, a current provided to the valve operator, and aninductive signature of the valve operator. The technique may furtherinclude determining, using the controller, one or more electricalparameters of the quantity of electrical power required by the valveoperator to hold the valve in the open state (428). The technique mayfurther include causing, using the controller, the determined one ormore electrical parameters to be delivered to the valve operator (430).

In an example, periodically determining the one or more electricalparameters includes decreasing, using the controller, the one or moreelectrical parameters until the valve deviates from the open state,thereby determining a closing amount of the one or more electricalparameters, and subsequently revising, using the controller, thequantity of electrical power provided to the valve operator based on theclosing amount of the one or more electrical parameters.

In examples, when a flame such as the pilot flame is in thermalcommunication with a gas flow, or a gas flow is in thermal communicationwith a flame, this means the flame generates a heat flux and the heatflux impinges on some portion of the gas flow. In examples, the heatflux of the flame is sufficient to generate combustion within theportion of the gas flow. In examples, when thermoelectric device 16 isin thermal communication with a flame, the flame generates a heat fluxand some portion of the heat flux impinges on some part ofthermoelectric device 16. In examples, the heat flux of the flame issufficient to cause thermoelectric device 16 to convert some portion ofthe heat flux into electrical energy.

In examples, one or more of pilot valve operator 12 and main valveoperator 14 are millivoltage automatic valve operators. In examples, oneor more of pilot valve operator 12 and main valve operator 14 areconfigured to alter the position of a valve when receiving power at lessthan 750 mV. In examples, one or more of pilot valve operator 12 andmain valve operator 14 cause the opening of a valve when in an energizedstate. In some examples, one or more of pilot valve operator 12 and mainvalve operator 14 cause the closing of a valve when in the de-energizedstate. In some examples, one or more of pilot valve operator 12 and mainvalve operator 14 control the energizing of an electromechanical devicesuch as a solenoid valve.

In examples, convertor 18 may be a power convertor which receiveselectrical power is a first form and converts the electrical power toanother form. Converter 16 may be an electronic circuit, electronicdevice, or electromechanical device. In examples, converter 16 receivesa first voltage received from thermoelectric device 16 and provides asecond voltage to electrical line 39. In examples, the second voltage isgreater than the first voltage. For example, convertor 18 might receivea first voltage of about 0.7 VDC (700 mV) from thermoelectric device 16and provide a voltage of about 3.3 VDC to electrical line 39. Inexamples, convertor 18 is a DC step-up convertor.

In examples, thermoelectric device 16 comprises one or more componentswhich generate an output voltage proportional to a local temperaturedifference or temperature gradient, such as a thermopile, thermocouple,or other thermoelectric generator. Thermoelectric device 16 may comprisea thermoelectric material. Thermoelectric device 16 may comprise aplurality of thermocouples connected in series or in parallel.Thermoelectric device 16 may comprise one or more thermocouple pairs. Inexamples, a heat flux from a pilot flame generates a temperaturegradient, and thermoelectric device 16 generates a DC voltage inresponse to the temperature gradient.

In examples, energy storage system 20 comprises one or more of acapacitor and a battery. Energy storage system 20 may comprise asupercapacitor. Energy storage system 20 may comprise an electrochemicaldouble-layer capacitor (EDLC). Energy storage system 20 may comprise oneor more of a double-layer capacitor, a pseudocapacitor, and a hybridcapacitor.

In examples, microcontroller 22 may include any one or more of amicrocontroller (MCU), e.g. a computer on a single integrated circuitcontaining a processor core, memory, and programmable input/outputperipherals, a microcontroller (μP), e.g. a central processing unit(CPU) on a single integrated circuit (IC), a controller, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field-programmable gate array (FPGA), a system on chip (SoC)or equivalent discrete or integrated logic circuitry. A processor may beintegrated circuitry, i.e., integrated processing circuitry, and thatthe integrated processing circuitry may be realized as fixed hardwareprocessing circuitry, programmable processing circuitry and/or acombination of both fixed and programmable processing circuitry.

In one or more examples, functions described herein may be implementedin hardware, software, firmware, or any combination thereof. Forexample, the various components and functions of FIGS. 1-5 may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on a tangiblecomputer-readable storage medium and executed by a processor orhardware-based processing unit.

Instructions may be executed by one or more processors, such as one ormore DSPs, general purpose microcontrollers, ASICs, FPGAs, or otherequivalent integrated or discrete logic circuitry. Accordingly, the term“processor,” as used herein, such as may refer to any of the foregoingstructure or any other structure suitable for implementation of thetechniques described herein. Also, the techniques could be fullyimplemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed.

The present disclosure includes the following examples:

Example 1: A water heater comprising: a thermoelectric device thatconverts thermal energy to electrical energy to power components of thewater heater; a valve configured to control whether there is a gas flowto cause a flame; and a controller configured to: receive power from theelectrical energy generated by the thermoelectric device; periodicallydetermine one or more electrical parameters for holding the valve in anopen state based at least in part on information indicative of whetherthe valve is in the open state; and cause a current to flow through thevalve based on the determined one or more electrical parameters.

Example 2: The water heater of example 1, wherein the informationindicative of whether the valve is in the open state is an amount of theelectrical energy generated by the thermoelectric device, and whereinthe controller is configured to determine the amount of the electricalenergy generated by the thermoelectric device.

Example 3: The water heater of example 1 or 2, wherein the informationindicative of whether the valve is in the open state is an increase or adecrease in the amount of the electrical energy generated by thethermoelectric device, and wherein the controller is configured todetermine the increase or the decrease in the amount of the electricalenergy generated by the thermoelectric device.

Example 4: The water heater of any of examples 1-3, wherein theinformation indicative of whether the valve is in the open state is atleast one of a voltage supplied to the valve, an inductive signature ofthe valve, or a current supplied to the valve, wherein the controller isconfigured to determine one or more of the voltage supplied to thevalve, the inductive signature of the valve, or the current supplied tothe valve.

Example 5: The water heater of any of examples 1-4, further comprising atemperature sensor, wherein the controller is configured to receive atemperature signal from the temperature sensor when the controllerperiodically determines the one or more electrical parameters.

Example 6: The water heater of example 5, wherein the controllerassociates the determined one or more electrical parameters with thetemperature signal.

Example 7: The water heater of example 6, wherein the controller causesthe current to flow through the valve based at least in part on thetemperature signal.

Example 8: The water heater of any of examples 1-7, wherein the valve isa solenoid operated valve comprising a solenoid and a plunger, andwherein when the controller causes the current to flow through thevalve, the current flows through the solenoid.

Example 9: The water heater of any of examples 1-8, wherein thethermoelectric device converts thermal energy from a pilot flame toelectrical energy, and wherein the gas flow is a main gas flow inthermal communication with the pilot flame, and wherein the flame is amain burner flame caused by the thermal communication between the pilotflame and the main gas flow.

Example 10: The water heater of example 9, wherein the pilot flame iscaused by a pilot gas flow and further comprising: a second valveconfigured to control whether there is the pilot gas flow, wherein thecontroller is configured to, periodically determine a second set of theone or more electrical parameters for holding the second valve in anopen state based at least in part on information indicative of whetherthe second valve is in the open state, and cause a current to flowthrough the second valve based on the determined second set of the oneor more electrical parameters.

Example 11: The water heater of example 10, further comprising: anenergy storage system, wherein the energy storage system is configuredto receive a first portion of the electrical energy from thethermoelectric device, wherein the second valve is configured to receiveelectrical energy from the energy storage system and configured toreceive a second portion of the electrical energy from thethermoelectric device, and wherein the valve is configured to receive athird portion of the electrical energy from the thermoelectric device.

Example 12: The water heater of any of examples 1-11, wherein the valveis configured to hold in the open state while receiving a holding amountof the one or more electrical parameters, and wherein the controller isconfigured to: determine when the valve deviates from the open state;provide the holding amount of the one or more electrical parameters andhold the valve in the open state; alter the one or more electricalparameters of the holding amount until the valve deviates from the openstate, thereby determining a dropping amount of the one or moreelectrical parameters; and revise the holding amount of the one or moreelectrical parameters based on the dropping amount of the one or moreelectrical parameters, thereby periodically determining the one or moreelectrical parameters for holding the valve in the open state.

Example 13: The water heater of example 12, wherein the controller isconfigured to determine when the valve deviates from the open stateusing at least one of the electrical energy generated by thethermoelectric device, a voltage supplied to the valve, an inductivesignature of the valve, or a current supplied to the valve.

Example 13: The water heater of examples 12 or 13, further comprising atemperature sensor, wherein the controller is configured to receive atemperature signal from the temperature sensor, and wherein thecontroller is configured to associate the revised sufficient amount ofthe one or more electrical parameters with the temperature signal.

Example 14: A water heater comprising: a thermoelectric deviceconfigured to convert thermal energy from a flame to generate electricalenergy to power components of the water heater; a valve having a valveoperator, wherein the valve operator is configured to receive electricalpower and cause the valve to hold an open state; a temperature sensor;and a controller configured to: receive power from the electrical energygenerated by the thermoelectric device when the flame is present andreceive power from a stored energy system when the pilot flame is notpresent; receive a temperature signal from the temperature sensor;periodically determine one or more electrical parameters of theelectrical power required by the valve operator to cause the valve tohold an open state based at least in part on information indicative ofwhether the valve is in the open state; associate the determined one ormore electrical parameters with the temperature signal; and provide theelectrical power to the valve operator based on the determined one ormore electrical parameters and the temperature signal.

Example 16: The water heater of example 15, wherein the controller isconfigured to: facilitate the electrical power to the valve operator andallow the valve operator to cause the valve to hold the open state;determine when the valve deviates from the open state; decrease, withthe valve in the open state, the one or more electrical parameters ofthe electrical power until the valve deviates from the open state,thereby determining a closing amount of the one or more electricalparameters; and revise the electrical power provided to the valveoperator based on the closing amount of the one or more electricalparameters and the temperature signal, thereby periodically determiningthe one or more electrical parameters of the electrical power requiredby the valve operator to cause the valve to hold the open state.

Example 17: The water heater of example 16, wherein the controller isconfigured to determine when the valve deviates from the open stateusing at least one of the electrical energy generated by thethermoelectric device, a voltage supplied to the valve operator, aninductive signature of the valve operator, or a current supplied to thevalve operator.

Example 18: The water heater of any of examples 15-17, wherein thethermoelectric device converts thermal energy from a pilot flame toelectrical energy, wherein the valve is configured to control a pilotgas flow causing the pilot flame, and further comprising: a second valveconfigured to control a main gas flow causing a main burner flame usingthe pilot flame, wherein the controller is configured to, periodicallydetermine a second set of the one or more electrical parameters forholding the second valve in the open state based at least in part oninformation indicative of whether the second valve is in the open state,and cause a current to flow through the second valve based on thedetermined second set of the one or more electrical parameters.

Example 19: A method comprising: generating electrical power using athermoelectric device converting thermal energy from a flame intoelectrical energy; delivering, using the controller, a quantity of theelectrical power to a valve operator configured to hold a valve in anopen state while receiving the quantity of electrical power; monitoring,using the controller, whether the valve is in the open state;determining, using the controller, one or more electrical parameters ofthe quantity of electrical power required by the valve operator to holdthe valve in the open state; and causing, using the controller, thedetermined one or more electrical parameters to be delivered to thevalve operator.

Example 20: The method of claim 19, further comprising: decreasing,using the controller, the one or more electrical parameters until thevalve deviates from the open state, thereby determining a closing amountof the one or more electrical parameters; revising, using thecontroller, the quantity of electrical power provided to the valveoperator based on the closing amount of the one or more electricalparameters, thereby periodically determining the one or more electricalparameters of the quantity of the electrical power required by valveoperator to hold the valve in the open state.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A water heater comprising: a thermoelectricdevice that converts thermal energy to electrical energy to powercomponents of the water heater; a valve configured to control whetherthere is a gas flow to cause a flame; and a controller configured to:receive power from the electrical energy generated by the thermoelectricdevice; periodically determine one or more electrical parameters forholding the valve in an open state based at least in part on informationindicative of whether the valve is in the open state; and cause acurrent to flow through the valve based on the determined one or moreelectrical parameters.
 2. The water heater of claim 1, wherein theinformation indicative of whether the valve is in the open state is anamount of the electrical energy generated by the thermoelectric device,and wherein the controller is configured to determine the amount of theelectrical energy generated by the thermoelectric device.
 3. The waterheater of claim 2, wherein the information indicative of whether thevalve is in the open state is an increase or a decrease in the amount ofthe electrical energy generated by the thermoelectric device, andwherein the controller is configured to determine the increase or thedecrease in the amount of the electrical energy generated by thethermoelectric device.
 4. The water heater of claim 1, wherein theinformation indicative of whether the valve is in the open state is atleast one of a voltage supplied to the valve, an inductive signature ofthe valve, or a current supplied to the valve, wherein the controller isconfigured to determine one or more of the voltage supplied to thevalve, the inductive signature of the valve, or the current supplied tothe valve.
 5. The water heater of claim 1 further comprising atemperature sensor, wherein the controller is configured to receive atemperature signal from the temperature sensor when the controllerperiodically determines the one or more electrical parameters.
 6. Thewater heater of claim 5 wherein the controller associates the determinedone or more electrical parameters with the temperature signal.
 7. Thewater heater of claim 6, wherein the controller causes the current toflow through the valve based at least in part on the temperature signal.8. The water heater of claim 1, wherein the valve is a solenoid operatedvalve comprising a solenoid and a plunger, and wherein when thecontroller causes the current to flow through the valve, the currentflows through the solenoid.
 9. The water heater of claim 1, wherein thethermoelectric device converts thermal energy from a pilot flame toelectrical energy, and wherein the gas flow is a main gas flow inthermal communication with the pilot flame, and wherein the flame is amain burner flame caused by the thermal communication between the pilotflame and the main gas flow.
 10. The water heater of claim 9 wherein thepilot flame is caused by a pilot gas flow and further comprising: asecond valve configured to control whether there is the pilot gas flow,wherein the controller is configured to, periodically determine a secondset of the one or more electrical parameters for holding the secondvalve in an open state based at least in part on information indicativeof whether the second valve is in the open state, and cause a current toflow through the second valve based on the determined second set of theone or more electrical parameters.
 11. The water heater of claim 10further comprising: an energy storage system, wherein the energy storagesystem is configured to receive a first portion of the electrical energyfrom the thermoelectric device, wherein the second valve is configuredto receive electrical energy from the energy storage system andconfigured to receive a second portion of the electrical energy from thethermoelectric device, and wherein the valve is configured to receive athird portion of the electrical energy from the thermoelectric device.12. The water heater of claim 1, wherein the valve is configured to holdin the open state while receiving a holding amount of the one or moreelectrical parameters, and wherein the controller is configured to:determine when the valve deviates from the open state; provide theholding amount of the one or more electrical parameters and hold thevalve in the open state; alter the one or more electrical parameters ofthe holding amount until the valve deviates from the open state, therebydetermining a dropping amount of the one or more electrical parameters;and revise the holding amount of the one or more electrical parametersbased on the dropping amount of the one or more electrical parameters,thereby periodically determining the one or more electrical parametersfor holding the valve in the open state.
 13. The water heater of claim12 wherein the controller is configured to determine when the valvedeviates from the open state using at least one of the electrical energygenerated by the thermoelectric device, a voltage supplied to the valve,an inductive signature of the valve, or a current supplied to the valve.14. The water heater of claim 12 further comprising a temperaturesensor, wherein the controller is configured to receive a temperaturesignal from the temperature sensor, and wherein the controller isconfigured to associate the revised sufficient amount of the one or moreelectrical parameters with the temperature signal.
 15. A water heatercomprising: a thermoelectric device configured to convert thermal energyfrom a flame to generate electrical energy to power components of thewater heater; a valve having a valve operator, wherein the valveoperator is configured to receive electrical power and cause the valveto hold an open state; a temperature sensor; and a controller configuredto: receive power from the electrical energy generated by thethermoelectric device when the flame is present and receive power from astored energy system when the pilot flame is not present; receive atemperature signal from the temperature sensor; periodically determineone or more electrical parameters of the electrical power required bythe valve operator to cause the valve to hold an open state based atleast in part on information indicative of whether the valve is in theopen state; associate the determined one or more electrical parameterswith the temperature signal; and provide the electrical power to thevalve operator based on the determined one or more electrical parametersand the temperature signal.
 16. The water heater of claim 15, whereinthe controller is configured to: facilitate the electrical power to thevalve operator and allow the valve operator to cause the valve to holdthe open state; determine when the valve deviates from the open state;decrease, with the valve in the open state, the one or more electricalparameters of the electrical power until the valve deviates from theopen state, thereby determining a closing amount of the one or moreelectrical parameters; and revise the electrical power provided to thevalve operator based on the closing amount of the one or more electricalparameters and the temperature signal, thereby periodically determiningthe one or more electrical parameters of the electrical power requiredby the valve operator to cause the valve to hold the open state.
 17. Thewater heater of claim 16 wherein the controller is configured todetermine when the valve deviates from the open state using at least oneof the electrical energy generated by the thermoelectric device, avoltage supplied to the valve operator, an inductive signature of thevalve operator, or a current supplied to the valve operator.
 18. Thewater heater of claim 15, wherein the thermoelectric device convertsthermal energy from a pilot flame to electrical energy, wherein thevalve is configured to control a pilot gas flow causing the pilot flame,and further comprising: a second valve configured to control a main gasflow causing a main burner flame using the pilot flame, wherein thecontroller is configured to, periodically determine a second set of theone or more electrical parameters for holding the second valve in theopen state based at least in part on information indicative of whetherthe second valve is in the open state, and cause a current to flowthrough the second valve based on the determined second set of the oneor more electrical parameters.
 19. A method comprising: generatingelectrical power using a thermoelectric device converting thermal energyfrom a flame into electrical energy; delivering, using the controller, aquantity of the electrical power to a valve operator configured to holda valve in an open state while receiving the quantity of electricalpower; monitoring, using the controller, whether the valve is in theopen state; determining, using the controller, one or more electricalparameters of the quantity of electrical power required by the valveoperator to hold the valve in the open state; and causing, using thecontroller, the determined one or more electrical parameters to bedelivered to the valve operator.
 20. The method of claim 19 furthercomprising: decreasing, using the controller, the one or more electricalparameters until the valve deviates from the open state, therebydetermining a closing amount of the one or more electrical parameters;revising, using the controller, the quantity of electrical powerprovided to the valve operator based on the closing amount of the one ormore electrical parameters, thereby periodically determining the one ormore electrical parameters of the quantity of the electrical powerrequired by valve operator to hold the valve in the open state.